In recent years, communication devices provided for a network often have a redundant configuration in order to upgrade system availability. In a redundant system, communication will be continued by activating a standby communication device when a fault has occurred in an active communication device that is in an active mode.
Further, as a technique for upgrading a security, for example, Security Architecture for Internet Protocol (IPsec) is used. With an IPsec, devices among which packets are transmitted are able to perform authentication, encryption, and exchange of encryption keys, and share the encryption keys with each other. In the case of using the IPsec in a system including redundant communication devices, for example, an encryption key is exchanged between an active communication device and an opposite node with which the active communication device is to communicate, and data communication between the active communication device and the opposite node is performed with elevated levels of security. When activating a standby communication device, for example, due to a fault occurrence in the active communication device, an encryption key is exchanged between the standby communication device and the opposite node.
Japanese Laid-open Patent Publication No. 2007-306562 discloses a method for switching between network media devices, in which copying reception switching parameters from a primary network media device to a redundant network media device is performed each time a specific amount of packets are received. The method allows the redundant media device to receive packets using the copied reception switching parameters.